Typical prior art bolted pipe coupling systems comprise a pair of flanged hubs having hub faces, a compression assembly for urging the hub faces together, and a sealing member disposed between the hub faces. When the compression assembly urges the hubs together, it forms a seal.
Such prior art couplings are limited in the materials with which they can be used. Because the gasket is oftentimes exposed to the materials flowing through the coupled pipes, care must be used to select the material of the gasket so as to not be dissolved, corroded, or otherwise destroyed by the flowing media. In many prior art couplings, the gasket serves as the only seal between abutted faces of the hubs.